Gas and electric-arc welding produces an extremely bright light that is rich in ultraviolet and infrared rays. Frequent or prolonged exposure to such light can blind a person. For this reason a helmet or goggles are usually worn by a welder, with a lens in the helmet or goggles provided with filters that stop the infrared and ultraviolet rays.
The principal difficulty with such a light-filtering lens or device is that visible light is also greatly attenuated. Thus it is customary for the welder to strike the arc or stop the welding operation with the goggles or helmet tilted up so that he can see what he is doing, and thereafter to put the goggles or helmet in place, as the light generated by the welding operation is thereafter then sufficient to allow him to see his work. This short but frequent exposure to the unfiltered light from the arc or flame is in the long run very harmful.